(a) Field of the Invention
The present invention relates to a charging method for rechargeable batteries and a device therefor, and more particularly to a charging method for rechargeable batteries and a device therefor using a constant current and a constant current pulse.
(b) Description of the Related Art
In general, a battery which is not reusable once it is discharged is referred to as a primary battery, and a battery which is rechargeable and reusable even when it is discharged is referred to as a secondary battery.
Recently, as portable devices, such as mobile phones, portable audio devices and digital cameras, have become widespread, the demand for rechargeable batteries has rapidly increased. A rechargeable battery used for these portable devices typically requires high stability and small thickness so that the battery is convenient to carry. In addition, such rechargeable batteries require fast and full charging to provide sufficient durability.
A typical charging method for rechargeable batteries used in these portable devices is a constant current mode-constant voltage mode charging method (referred to as “CC-CV charging method” hereinafter). The CC-CV charging method is a method of charging the rechargeable battery with a constant current until the voltage of the battery is increased to near full charging potential, after which the battery is charged with a constant voltage.
Charging methods to enable more precise and faster full charging over such a CC-CV charging method have been studied. As one example of these charging methods, U.S. Pat. No. 4,736,150 discloses a method of charging the battery by applying a pulsed current having a frequency range of 0.1 to 10 Hertz to the battery at an interval of 1 ms to 9 s. This method has an advantage in that the lifetime of the battery is prolonged because the battery is charged using a current with particular amplitude and frequency. However, this method has a disadvantage in that, because the battery is charged by applying the pulsed current to the battery for the entire charging period, the charging time is long.
U.S. Pat. No. 3,938,019 discloses a method of charging the battery by applying constant current to the battery until a charging voltage of the battery reaches a predetermined voltage, after which a constant current pulse is applied to the battery. This method enables faster and fuller charging than the method disclosed in U.S. Pat. No. 4,736,150.
As a variety of portable devices having high power consumption are rapidly increasing, interest in batteries used by these devices continues to increase. Therefore, there is a need for an improved charging method and device to enable faster and more stable full charging.